Resonant window and method of making same



July 13, 1954 T. P. CURTIS RESONANT WINDOW AND METHOD OF MAKING SAME v Filed April 2, 1951 Fig. I.

Ifiventor: Truman P Cu rtis,

b my) His Attorney Patented July 13, 1954 RESONANT WINDOW AND METHOD OF MAKING SAME Truman P. Curtis, Scotia, N. Y., assignor to General Electric Company, a corporation of New York Application April 2, 1951, Serial No. 218,840

3 Claims.

My invention relates to an improved resonant window structure and an improved method of making such structures.

In high-frequency apparatus, it is often desirable to physically separate one part of the apparatus from another by a wall having predetermined electrical characteristics with respect to the operating frequency of the apparatus. More particularly, it is desirable to provide a wall section which is vacuum-tight, made up of a dielectric plate such as glass or ceramic, having a surface area framed by a conducting member, dimensioned to provide a resonant opening or window. Windows of this general character have been used in wave guides, such as the output wave guide of an electric discharge device, in order to provide for the transmission of energy from the device and, at the same time, complete the wall of the vacuum-tight envelope. These windows have also been used in high frequency gaps known in the art as transmit-receive and anti-transmit receive devices, for use in connection with transmitting and receiving apparatus coupled to a Single antenna.

It is an object of the present invention to provide a structure for windows of the above type and an improved method of manufacturing such windows, which is particularly suited to the use of ceramics as the dielectric member, and characterized further by the ease of manufacture and attainment of the accurate dimensions required for establishing the resonant frequency of the window.

Further objects and advantages of my invention will become apparent as the following description proceeds and its scope will be pointed out in the appended claims. In the drawing, Fig. 1 is a perspective view of a Wave guide terminating in a window embodying the present invention; Fig. 2 is a sectional View taken along the line 2-2 of Fig. 1; and Fig. 3 is an elevational view of the dielectric window metallized in accordance with the present invention prior to assembly in the wave guide.

Referring now to the drawing, my invention is there illustrated as embodied in a window structure I for a wave guide 2 of the rectangular hollow pipe type. The window includes a metallic frame 3 having a rectangular opening 4 in the end thereof and an outwardly extending flange 5 at the opposite end for joining with a corresponding flange 6 formed on the wave guide. The resonant opening or window I is defined by a metallized coating 8 on the surface of a dielectric plate 9 which is joined to and supported from the frame 3.

The improved method of making the device described above in accordance with the present invention will now be described. A generally rectangular dielectric plate 9, as shown in Fig. 3, is preferably provided with a beveled edge l0 and is provided with a tightly adhering metal coating H on the marginal area of one face thereof and also on the outer edge, if desired. This coating may be applied in accordance with any of the known processes for metallizing the material of the window. If the window is of ceramic, the metallizing may be done to advantage by the manganese method, which is described in detail in the copending application Serial No. 722,049 filed January 14, 1947, and as signed to the assignee of this invention. In accordance with the method there described, a mixture of manganese and a powder selected from the group consisting of molybdenum, iron, tungsten, and nickel, but preferably consisting of molybdenum, is mixed with a quantity of elemental manganese and painted or sprayed on the surface to be metallized. It is apparent that by use of a suitable template that the area to be covered by the metallized coating is readily controlled so that the dimensions of the window opening I are subject to accurate determination during the manufacturing operation.

The resultant plate, after the coating has been applied, is heated in a hydrogen atmosphere to a temperature in the order of 1400" C. for a period of 5 to 15 minutes, to provide the tightly adhering coating. The finished product is then in suitable condition for brazing by a silver brazing process, for example, to the inwardly directed flange of the frame 3. By producing the window with a metallized surface on the marginal portion of one side only, the entire area of the dielectric plate on the opposite side is available as an insulating surface across the interior of the wave guide. The metallizing may be readily ground off, even after assembly of the device, for the purpose of changing the resonant frequency of the'window or for making final adjustment in that frequency.

This adjustment in frequency is readily made, since the actual dimensions of the opening are increased by grinding off along the ends or sides of the opening defined by the coating. This method of tuning is obviously much simpler and more effective than such prior art methods as using adjustable mechanical devices in conjunction with the window of actually grinding the composite glass and metal structure to a lesser thickness.

Instead of the manganese-molybdenum method of metallizing described above, it is also possible to use the titanium hydride method de scribed and claimed in copending application Serial No. 36,244Bondley, filed June 30, 1948, and assigned to the assignee of this invention. In accordance with that method, the area to be metallized is painted with powdered titanium hydride in a suitable carrier or binder, and the parts assembled in the final position. A body of solder is placed in position to melt and fiow into contact with the coated area when it is melted. This assembly is heated in a vacuum to a temperature suificient to dissociate the hydride and melt the solder, so that the metallizing and bonding of the dielectric plate into the frame may be accomplished in one operation.

It is apparent from the foregoing that my invention provides an improved structure for windows of the resonant type, which is readily manufactured and which provides for the attainment of the desired operating frequency of the device by simply grinding off a small amount of the metallized coating.

While I have described and claimed a particular embodiment of my invention, it will be apparent to those skilled in the art that changes and modifications may be made without departing from my invention in its broader aspects, and I intend in the appended claims to cover all such changes and modifications as fall within the true scope and spirit of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A resonant window for high frequency apparatus comprising a window member of dielectric material, a metallic coating on one face of said window member defining a resonant opening, a metal frame joined to said member and having an opening registering with and substantially larger than the opening defined by said metallic coating.

2. The method of making a resonant window of high frequency electrical apparatus which comprises the steps of applying a tightly adhering metal coating to a marginal area of one face of a plate of dielectric material to define a resonant opening, joining a metal supporting frame to a part of the coated area and leaving an area of the coating surrounding the resonant opening exposed so that the resonant frequency of the window is determined by the area of the opening in the metallized coating and removing metal from the edges of the opening in the metal coating to determine the resonant frequency of the window.

3. A resonant window for high frequency electrical apparatus comprising, a window member of dielectric material, a tightly adhering metal coating on the marginal area of one face of said window member defining a resonant opening, a metal supporting frame joined to a part of the coated area and having an opening registering with and substantially larger than the opening defined by said metal coating.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,151,686 Briefer Mar. 28, 1939 2,467,730 Coltman Apr. 19, 1949 2,523,155 Shoupp Sept. 19, 1950 

